/**
 * Definition for singly-linked list.
  **/
 class ListNode {
     int val;
      ListNode next;
      ListNode() {}
      ListNode(int val) { this.val = val; }
      ListNode(int val, ListNode next) { this.val = val; this.next = next; }
  }
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode cur = head;
        if(head == null){
            return head;
        }else if(head.next == null){
            return head;
        }
        while(cur.next != null){
            if(cur.val == cur.next.val){
                cur.next = cur.next.next;

            }else{
                cur = cur.next;
            }
        }
        return head;
    }
}